1. Field of the Invention
The present invention relates to microwaves plasma lamp apparatuses and, more particularly, to a microwaves lamp apparatus that independently performs impedance matching and generates elliptically polarized microwaves.
2. Description of the Related Art
Since a conventional high intensity discharge (HID) lamp uses electrodes, its lifetime is limited to a few thousand hours. The end-of-life behaviors of the conventional HID lamp include a rapid decrease in the light flux. Moreover, since the conventional HID lamps use mercury that is one of the hazardous materials for the environment.
High-power microwaves HID lamps have emerged to overcome the foregoing disadvantages. A conventional high-power microwave discharge lamp that was disclosed to circumvent the above-mentioned problems uses a cylindrical waveguide in which a TE11 mode is excited, which is the lowest fundamental mode in a cylindrical waveguide. Accordingly, a spherical bulb is inserted in the cylindrical waveguide, and the shape of the plasma in the bulb is formed according to the pattern of the electric field lines in the TE11 mode. Since the electric field lines in the TE11 mode is almost linear, the plasma discharges are formed in an oval shape in the bulb. Thus, in case of high-power discharges, the hot plasma may cause local heating in the spherical bulb and the spherical bulb may be easily punctured due to the local heating.
In order to overcome the puncture caused by local heating, the bulb is rotated using a mechanical motor in the prior art lamps. This is not a desirable feature for any lamp. Another method has been proposed to rotate the electric field applied to the spherical lamp, facilitating the generation of uniform plasma discharges in a stationary bulb.